1. Field of the Invention
This invention relates to a process for forming a molded plastic layer on a metal plate.
2. Description of the Related Art
For various purposes, molded articles may include a patterned molded plastic layer and a metal piece that is enclosed in the molded plastic layer. In order to form the molded plastic layer on the metal piece, there is a need to support the metal piece in the mold so that the metal piece separates the mold cavity into two sub-cavities at two opposite sides of the metal piece such that subsequent introduction of a resin in the mold permits the formation of the molded plastic layer. However, undesirable holes formed in the molded plastic layer due to the presence of the supporting means which supports the metal piece in the mold. Moreover, when a pattern is to be formed on the molded plastic layer, the holes will undesirably limit the flexibility of the pattern design.
Therefore, the object of the present invention is to provide a process for forming a molded plastic layer on a metal plate that is capable of overcoming the aforementioned drawbacks.
According to the present invention, there is provided a process for forming a molded plastic layer on a metal plate. The process comprises the steps of: preparing a first mold that confines therein a first mold cavity and that has first upper and first lower mold halves which have first upper and first lower inner walls defining the first mold cavity, the first upper and first lower inner walls being formed with a plurality of pairs of complementary upper and lower post forming grooves and a plurality of pairs of complementary upper and lower positioning protrusions that project into the first mold cavity; forming a plurality of post forming holes and a plurality of positioning holes in the metal plate; placing the metal plate in the first mold cavity such that each pair of the complementary upper and lower positioning protrusions extend into a respective one of the positioning holes and such that each pair of the complementary upper and lower post forming grooves are vertically registered with and cooperate with a respective one of the post forming holes to define a post forming cavity; introducing a first resin into the post forming cavities to form a plurality of supporting posts that respectively extend through the post forming holes and that are bonded to the metal plate, the supporting posts cooperating with the metal plate to form an intermediate product; preparing a second mold that defines therein a second mold cavity and that has second upper and second lower mold halves which have second upper and second lower inner walls defining the second mold cavity; placing the intermediate product in the second mold cavity such that the supporting posts abut against the second upper and second lower inner walls and such that the metal plate partitions the second mold cavity into upper and lower mold sub-cavities; and introducing a second resin into the upper and lower mold sub-cavities to form a molded part that is bonded to and that cooperates with the supporting posts to form the molded plastic layer which encloses the metal plate.